The present invention relates to a rotary electric machine which is high in material use factor of a rotor core and small in size and light in weight, and to an electric vehicle using the rotary electric machine.
A motor used for an electric drive vehicle is desired to be small in size, light in weight and high in efficiency. Making size of a motor small can be attained by rotating the motor at high speed. From this viewpoint, drive motors suitable for an electric vehicle such as an electric car, a battery forklift or the like are, firstly, a motor of a permanent magnet type and, secondary, a brushless motor using reluctance. Particularly, the reluctance motor is inferior to a magnet motor using a high performance magnet in efficiency and torque, but is nearly equivalent to a magnet motor using a ferrite magnet. The reluctance motor, however, has an advantage in that there are no problems such as temperature dependence of the characteristic, demagnetization of the magnet and that the motor is economical and practical.
A reluctance motor of the prior art is described in an article entitled xe2x80x9cA magnetic field analysis of a flux barrier type reluctance motor using a slit rotor and tests using a prototypexe2x80x9d, Journal of Electrical Engineers of Japan (June, 1996). The motor has such a structure that the rotor is formed by laminating magnetic plates such as silicon steel plates in the axial direction and the rotor is formed using silicon steel plates in an integrated body.
The conventional technology described above is advantageous in that the material use factor at manufacturing the stator core is improved since the stator core is divided, but is disadvantageous in that the material use factor of the rotor is poor since the rotor is formed in a single body. The central core portion of the rotor, particularly in the flat shaped rotor, is practically unnecessary because the magnetic flux density at that portion is low. Since the portion is, however, filled with the material, a quantity of the material for forming the rotor is increased and accordingly the weight of the motor is increased.
In addition to this, the increase in the weight becomes a large load for the electric vehicle or the electric drive car.
On the other hand, Japanese Patent Application Laid-Open No. 9-74713 discloses a permanent magnet type rotary electric machine in which the bearing and the differential gear are arranged inside the rotor by increasing the inner diameter of the rotor to make the motor compact.
The above-mentioned technology does not investigate on shapes of the rotor and the stator, and particularly the optimized value for the inner diameter of the rotor is not shown.
When the inner diameter of the rotor is increased, the weight of the rotor itself is decreased and accordingly the weight of the motor (the rotor and the stator) becomes lighter. In addition, it becomes easy to arrange the bearing and so on inside the inner portion of the rotor. However, when the distance r between the permanent magnet and the inner diameter of the rotor is small, the magnetic flux density is decreased by interfering with flow of the magnetic flux. Therefore, there is a disadvantage in that the weight of the motor is increased since the laminating thickness needs to be increased in order to keep the output power high even if the gap magnetic flux density is decreased.
In recent years, the permanent magnet type rotary electric machine has been growingly used for a drive motor of a hybrid electric vehicle. Since the hybrid electric vehicle needs to mount a drive motor, a battery and an engine, reduction of weight is the most important problem, and reduction of weight of the drive motor is an important problem as a matter of course.
An object of the present invention is to provide a rotary electric machine which is high in material use factor at manufacturing a rotor core and small in size and light in weight, and to provide an electric vehicle using the rotary electric machine.
Another object of the present invention is to provide a permanent magnet type rotary electric machine capable of reducing the weight of the motor without decreasing the output power of the motor.
In order to attain the above-mentioned objects, a feature of a rotary electric machine in accordance with the present invention is that a rotor core comprising a plurality of projecting poles arranged in a side of a gap and along the circumferential direction and a plurality of rotor yokes for forming a magnetic path conducting magnetic fluxes of each of the projecting poles is divided in the circumferential direction in a unit of each of the projecting poles and each of the rotor yokes opposite to each of the projecting poles.
In more detail, the present invention provides the following rotary electric machines.
The present invention provides a rotary electric machine comprising a stator having a stator core wounded with stator windings; and a rotor having a rotor core rotatable and opposite to the stator core through a gap, wherein the rotor core comprises a plurality of projecting poles arranged in a side of the gap and along the circumferential direction; and a plurality of rotor yokes for forming a magnetic path conducting magnetic fluxes of each of the projecting poles, and the rotor core is divided in the circumferential direction on a unit of each of the projecting poles and each of the rotor yokes opposite to each of the projecting poles.
It is preferable that a position of the division is at each middle position of width in the circumferential direction of the projecting poles.
Further, the present invention provides a rotary electric machine comprising a stator having a stator core wounded with stator windings; and a rotor having a rotor core rotatable and opposite to the stator core through a gap, wherein the rotor core comprises a plurality of permanent magnets arranged and embeded therein in a side of the gap and along the circumferential direction; and a plurality of rotor yokes for forming a magnetic path conducting magnetic fluxes of each of the permanent magnets, and the rotor core is divided in the circumferential direction in a unit of each pole of the permanent magnets and each of the rotor yokes opposite to each pole of the permanent magnets.
It is preferable that a position of the division is at each position between the poles of the permanent magnets.
It is preferable that the rotor core is made of a different material from a material of the stator core.
Furthermore, the present invention provides an electric vehicle comprising a battery for supplying electric power; a rotary electric machine for outputting drive torque to drive the vehicle by the supplied electric power; and a controller for controlling the drive torque, wherein the rotary electric machine comprises a stator having a stator core wounded with stator windings; and a rotor having a rotor core rotatable and opposite to the stator core through a gap, and the rotor is formed of a rotor core divided in the circumferential direction in a unit of each magnetic pole and a holding member having an I-shaped cross section for holding the rotor core, the holding member having an I-shaped cross section being disposed an inner peripheral side of the rotor core in order to lengthen a driving distance per charge of the vehicle by reducing the vehicle weight.
Further, in order to attain the above-mentioned objects, a feature of a permanent magnet type rotary electric machine in accordance with the present invention is that the relation r/w≈0.6xc2x10.1 is satisfied where r is a distance in a radial direction from an inner radial surface of the rotor core to a side end portion between poles of an inner peripheral surface of each of the permanent magnets, and 2xc2x7w is a length in the circumferential direction of the permanent magnet.
In more detail, the present invention provides the following rotary electric machines.
The present invention provides a permanent magnet rotary electric machine comprising a stator having a stator core wounded with stator windings; and a rotor having a rotor core opposite to the stator core through a rotation gap, a plurality of permanent magnets being arranged and embeded in the rotor core in the circumferential direction, wherein the relation r/w≈0.6xc2x10.1 is satisfied where r is a distance in a radial direction from an inner radial surface of the rotor core to a side end portion between poles of an inner peripheral surface of each of the permanent magnets, and 2xc2x7w is a length in the circumferential direction of the permanent magnet.
Further, the present invention provides a permanent magnet rotary electric machine comprising a stator having a stator core wounded with stator windings; and a rotor having a rotor core opposite to the stator core through a rotation gap, a plurality of permanent magnets being arranged and embeded in the rotor core in the circumferential direction, the rotor core having a plurality of die-cut holes in the circumferential direction between an inner radial surface of the rotor core and an inner peripheral surface of the permanent magnets, wherein the relation t/w≈0.6 is satisfied where t is a distance in a radial direction from the permanent magnet side of each of the die-cut holes to a side end portion between poles of an inner peripheral surface of each of the permanent magnets, and 2xc2x7w is a length in the circumferential direction of the permanent magnet. Therein, the words xe2x80x9cradial directionxe2x80x9d means a direction from the center of a shaft of the rotor core toward the outer diameter of the rotor core, as to be described in the section of DESCRIPTION OF THE PREFERRED EMBODIMENTS.